Work clamp for sewing machines

ABSTRACT

A work clamp for holding a fabric in tensioned conditioning during the sewing of stitches thereon. The clamp comprises opposed pivoted members which incline relative to the sewing plane when the clamp is lifted to an inoperative position. These members gradually grip the work fabric and tension it as they assume a parallel position relative to the sewing plane in consequence of the clamp being lowered to a working position.

United States Patent Bianchi 1 1 Jan. 30, 1973 [54] WORK CLAMP FOR SEWING [56] p I Rgf erenges cjted V p 7 N MACHINES UNITED STATES PATENTS [751 Blanch, Pavia Italy 875,622 12/1907 Parkes ..ll2/76 73 Assigneez Necchi Sm-A Pavia, Italy 789,l26 5/l905 Gatchell 1 ..l 12/76 [22] Filed: Jan- 5, 1971 Primary Examiner-H. Hampton Hunter [211 App]. NOJ 104,049 Attorney-Stevens, Davis, Miller & Mosher [57] ABSTRACT [30] Apphcat'on Pnonty Data A work clamp for holding a fabric in tensioned condi- Jan.28, 1970 Italy ..4290l A/70 Ii ning during the sewing of stitches thereon. The clamp comprises opposed pivoted members which 52 11.5. (:1 ..ll2/76 incline relative to the Sewing Plane when the clamp is 511 1111.01. ..D05b.27/04, DOSb 29/08 lifted 10 an inoperative positioh- These members 58 Field of Search ..l12/76, 77, 70, 19, 207, 90, gradually p the work fabric and tension it as y 112/102, 118, l2l.l5, l2l.26,204, 205

assume a parallel position relative to the sewing plane in consequence of the clamp being lowered to a working position.

3 Claims, 3 Drawing Figures WORK CLAMP FOR SEWING MACHINES This invention relates to an improved work clamp for holding fabric during the sewing of stitches thereon, and particularly suited for application to a sewing machine which sews welted pockets.

In order to make a welted pocket, it is necessary to place a piece of base fabric on a work plate which is displaceable in a straightline under the needle and along the longitudinal axis of the sewing machine, and to secure said piece of fabric on the work plate by means of a work clamp adapted to follow work plate movement.

A piece of patch fabric is then placed onto the work clamp and positioned by means of a pair of cooperating side pressers under a center blade. The side pressers are adapted to follow movement of the work plate while the center blade is in a fixed position relative to the sliding movement of the work plate. Maintaining the work plate at rest, and first causing the center presser to lower and then causing the side pressers to converge towards the center presser, a patch fabric takes the shape of an inverted T between the side pressers and the center presser, the side edges of the fabric being turned upwards and brought near each other. Then, the work plate, the work clamp and side pressers are displaced along the longitudinal axis of the bed of the sewing machine, so displacing the fabric relative to a pair of sewing needles to form two parallel longitudinal lines of stitches thereon. During displacement of the fabric, a cutter which is actuated by needle bar cuts a slit parallel to the lines of stitches. Preferably, the slit is located mid-way between the two lines of stitches. The machine stops operating when the lines of stitches and the slit have been completed. The work plate, however, continues its movement and stops upon arrival at patch turners and tab slit cutters. Said patch turners and tab slit cutters then move upwards to make two cuts, having the shape of a 90 inverted V joining each of the two ends of the slit to the corresponding pair of sewing ends. Subsequently, the patch turners and tab slit cutters make a backward stroke to turn the tabs inside out.

During the loading of the sewing machine it may occur that the fabric positioned between the work plate and the work clamp is not well tensioned. This condition cannot be corrected by lowering a work clamp of the usual type, therefore, at the end of the sewing cycle, the patch pocket obtained will be wrinkled.

An object of the present invention is to overcome the aforementioned drawback. In this regard, the technical problem to be solved was that of designing a new work clamp which, during clamping of the fabric between the work clamp and the work plate, operates in such a way as to tension the fabric.

A new fabric work clamp has therefore been developed characterized in that it comprises two adjacent portions, having inner ends facing each other, suitable to assume, in their idle position of fabric loading on the machine, an inclination relative to the sewing plane; said facing ends thus taking a position higher relative to the outer ends, which are this way pre-arranged first to come into contact with the fabric and tension it owing to their displacement outward which is caused by the rotation and the lowering of said portions when they move from their idle position to their working position.

A further advantage is obtained by the present work clamp in that it is provided with two distinct presser members, everyone free to rotate around a proper pin to adapt its respective pressing surface on the fabric.

This constructive feature permits the obtaining of a more uniform pressure on the fabric and, consequently, a more accurate execution of the sewing, cutting and folding of the fabric described hereinabove.

This result is obtained because, increasing the number of pressing members of the work clamp reduces the drawbacks accruing from lack of planarity which is unavoidable in the manufacturing of the work clamp of a single sole of a considerable size, which drawbacks may result in wide parts of the pressing surface being practically free of pressure. In such parts the sewing, cutting and folding operations can be imperfeet.

The features and advantages set forth above will be apparent from the description and from the attached drawings referring to a particular embodiment not restrictive of the invention in which:

FIG. 1 is an elevation view of the sewing machine on which the present work clamp is mounted;

FIG. 2 is a plan view of said work clamp; and,

FIG. 3 is an elevation view of the work clamp of FIG.

Referring to FIG. 1, 10 indicates a sewing machine for making welted pockets, said machine comprising a bed 11, a base 12, a standard 13, an arm 14 parallel to said bed 11 and a head 15 from which needle bar 43 projects, carrying a pair of needles 44 suitable to form onto the fabric two parallel longitudinal lines of stitches and a cutter 45 driven by said needle bar movable together with said needles to cut a slit in the fabric parallel to the lines of stitches and mid-way between them. At one end of the upper shaft 16 two pulleys l7 and 18 are mounted suitable to receive the driving belt, not shown in the drawings, connected to the electric motor of the sewing machine. The passage of the belt from pulley 17 integral with shaft 16, to pulley 18, idly mounted on said shaft, is obtained by means of a beltshifter strictly connected to a well-known lock device generally indicated at 19. A rod 20 is connected to said lock device 19 and is slidable on the upper part of the arm 14, whose front end acting on the opposed axis of two known thread devices 21 when the machine is locked neutralizes the tension normally exerted by these devices on the sewing threads. A work plate 22, schematically shown in FIG. 3, is slidable mounted on the bed 11 and is driven by pistons of double acting pneumatic cylinder 23 (FIG. 1) and of an oleo-dynamic control cylinder 24, said control cylinder 24 being adapted to regulate and render uniform the speed of displacement of work plate 22. A work clamp 25, suitable to fasten onto work plate 22 a piece of fabric not shown in the drawings is connected by means of a pair of levers 26 to work plate 22 in order to follow work plate movement as described more in detail in our U.S. Pat. application Ser. No. 58,577 ofJuly 27, 1970.

A pair of lateral presser members 27 and a center blade 28 are provided to place onto the fabric a piece of patch fabric folded in a suitable way.

Work clamp 25 (FIGS. 2 and 3) is formed by two portions. The first one is an inverted U-shaped member 29 having chamfered ends 30 while the second one is formed by two plates 31 having, chamfered ends 32 in front of said member 29, similar to ends 30. Plates 31 are connected to member 29 by means of rods 33 pivoted to freely rotate at 34 and 35 on blocks 36 and 37 fastened to said plates 31 and to said member 29, respectively, by means of screws 38. Said rods 33 are also connected to levers 26 by means of pins 39.

When work clamp 25 is raised from work plate 22 to place fabric in work position, member 29 and plates 31 rotate so as to bring their chamfered portions 30 and 32 into contact with lower surfaces 40 of rods 33 respectively. This rotation allowed by the presence of said chamfered portions 30 and 32, takes place around pins 35 and 34 and is caused by the weight of the parts of member 29 and of plates 31 to one side of pins 35 and 34, being heavier than the load of these parts on the other side of said pins and, moreover, is helped by the four springs 41, each in a hole 42 made out in each end of each rod 33 (in FIG. 3 only one spring is shown). Said springs are positioned relative to pins 35 and 34 in such a way as to allow the rotation of member 29 and of plates 31 in the way mentioned above.

After positioning of the piece of fabric onto work plate 22, work clamp 25 is lowered as to reach the position shown in FIG. 3.

During lowering of the work clamp, the fabric is first contacted by outer ends of members 29 and of plates 31 because of the inclination of same, and then said member 29 and plates 31 become horizontal in order to press the fabric onto work plate 22.

In attaining the working position, the outer ends of member 29 and of plates 31 move outward exerting a dragging or pulling action on the fabric to tension it, thereby eliminating any wrinkles therein normally caused by the rigid lowering of the work clamps used previously, as would occur if the fabric had not been positioned carefully onto the work clamp.

What is claimed is:

l. A fabric work clamp especially for sewing machines adapted to sew patch pockets, said clamp comprising:

a support means, a first and a second elongate fabricgripping plate means, each comprising respective inner ends adjacent to and facing each other and respective outer ends at opposite extremes to each other with said plate means being in a coplanar position in the fabric-gripping position, said first and second fabric-gripping plate means being pivotally supported on said support means eccentrically to the center of gravity of each said plate means whereby each said means is freely pivotable by gravity from said coplanar position in a direction such that said inner ends move upwardly away from each other while said outer ends move downwardly towards each other, said outer ends in turn being adapted to grip respective spaced apart portions of a work fabric and to spread same apart pursuant to said plate means being pivoted in respective directions contrary to the urging of gravity towards said coplanar position, said support means bridging across said inner ends of said first and second plate means, said first and second plate means being pivotally mounted to respective spaced apart points on said support means, a vertical space existing between said inner ends and said sup ort meanswith said plate means being in said cop anar position, the extent to which said plate means are freely pivotable by gravity being limited by the extent of said vertical space, said first plate means comprising a U-shaped member having spaced apart legs and said second plate means comprising two parallel elongate plates aligned respectively as longitudinal prolongations of said legs, said inner ends being comprised by the free ends of said legs and by the thereto adjacent end portions of said plates, said support means comprising two rods respectively bridging across from the inner end portion of a said plate to the inner end portion of a therewith aligned one of said legs, each said leg and a therewith aligned one of said plates being pivotally supported on a respective one of said rods at longitudinally spaced apart points thereon, said rods being substantially parallel to said legs and to said plates, said space existing between said rods and said legs and plates in the longitudinal extent between said spaced pivot points whereby said U-shaped member and plates may simultaneously pivot from a coplanar position as aforementioned.

2. The clamp of claim 1, said recess being formed by said legs and plates having longitudinally inclined upper surfaces from their adjacent ends to the area at which they are pivotally supported on said rods.

3. The' clamp of claim 1, including a resilient biasing means urging said plate means to pivot in the direction in which gravity urges said plate means to pivot. 

1. A fabric work clamp especially for sewing machines adapted to sew patch pockets, said clamp comprising: a support means, a first and a second elongate fabric-gripping plate means, each comprising respective inner ends adjacent to and facing each other and respective outer ends at opposite extremes to each other with said plate means being in a coplanar position in the fabric-gripping position, said first and second fabric-gripping plate means being pivotally supported on said support means eccentrically to the center of gravity of each said plate means whereby each said means is freely pivotable by gravity from said coplanar position in a direction such that said inner ends move upwardly away from each other while said outer ends move downwardly towards each other, said outer ends in turn being adapted to grip respective spaced apart portions of a work fabric and to spread same apart pursuant to said plate means being pivoted in respective directions contrary to the urging of gravity towards said coplanar position, said support means bridging across said inner ends of said first and second plate means, said first and second plate means being pivotally mounted to respective spaced apart points on said support means, a vertical space existing between said inner ends and said support means with said plate means being in said coplanar position, the extent to which said plate means are freely pivotable by gravity being limited by the extent of said vertical space, said first plate means comprising a U-shaped member having spaced apart legs and said second plate means comprising two parallel elongate plates aligned respectively as longitudinal prolongations of said legs, said inner ends being comprised by the free ends of said legs and by the thereto adjacent end portions of said plates, said support means comprising two rods respectively bridging across from the inner end portion of a said plate to the inner end portion of a therewith aligned one of said legs, each said leg and a therewith aligned one of said plates being pivotally supported on a respective one of said rods at longitudinally spaced apart points thereon, said rods being substantially parallel to said legs and to said plates, said space existing between said rods and said legs and plates in the longitudinal extent between said spaced pivot points whereby said U-shaped member and plates may simultaneously pivot from a coplanar position As aforementioned.
 1. A fabric work clamp especially for sewing machines adapted to sew patch pockets, said clamp comprising: a support means, a first and a second elongate fabric-gripping plate means, each comprising respective inner ends adjacent to and facing each other and respective outer ends at opposite extremes to each other with said plate means being in a coplanar position in the fabric-gripping position, said first and second fabric-gripping plate means being pivotally supported on said support means eccentrically to the center of gravity of each said plate means whereby each said means is freely pivotable by gravity from said coplanar position in a direction such that said inner ends move upwardly away from each other while said outer ends move downwardly towards each other, said outer ends in turn being adapted to grip respective spaced apart portions of a work fabric and to spread same apart pursuant to said plate means being pivoted in respective directions contrary to the urging of gravity towards said coplanar position, said support means bridging across said inner ends of said first and second plate means, said first and second plate means being pivotally mounted to respective spaced apart points on said support means, a vertical space existing between said inner ends and said support means with said plate means being in said coplanar position, the extent to which said plate means are freely pivotable by gravity being limited by the extent of said vertical space, said first plate means comprising a U-shaped member having spaced apart legs and said second plate means comprising two parallel elongate plates aligned respectively as longitudinal prolongations of said legs, said inner ends being comprised by the free ends of said legs and by the thereto adjacent end portions of said plates, said support means comprising two rods respectively bridging across from the inner end portion of a said plate to the inner end portion of a therewith aligned one of said legs, each said leg and a therewith aligned one of said plates being pivotally supported on a respective one of said rods at longitudinally spaced apart points thereon, said rods being substantially parallel to said legs and to said plates, said space existing between said rods and said legs and plates in the longitudinal extent between said spaced pivot points whereby said U-shaped member and plates may simultaneously pivot from a coplanar position As aforementioned.
 2. The clamp of claim 1, said recess being formed by said legs and plates having longitudinally inclined upper surfaces from their adjacent ends to the area at which they are pivotally supported on said rods. 